Contact point sensing from force measurements disturbed by noise

This paper considers a method to determine a contact point location between two rigid bodies, a robot and an object, by a 6-axis force/moment sensor. In the noiseless case, it is well known that the contact point location can be determined directly by solving equations representing the force/moment balances for the exerted force and the resultant sensor signals. Although we can substitute the measured signals to the solution whether noise exists or not, if the noise exists, minimizing solution for the error of the force/moment balances will be preferable. In this paper, we formulate the estimation problem as the minimization problem of the weighted sum of the error of the force/moment balances. The optimization problem is solved analytically and the solution is derived in a closed form. Candidates of the contact point are represented by a line, which is parallel to the estimated acting force. The proposed method is also extended to the case where the measurement signals for multiple sampling instants can be utilized. A numerical example and experiments are shown to prove effectiveness of the proposed method.